The invention relates to the thrust swivel bearings on mowing knives supported in swing arms of mower cutting systems with reciprocating mowing knives of various types by means of which bearings the knives are always resiliently pressed on in the cutting region for the cutting contact.
Mower cutting systems of this kind with one or two reciprocating mowing knives serve the purpose of cutting stalky crops, such as, grass, clover, corn or the like, without clogging while requiring little maintenance.
For reaching this goal, it is known from West German Patent No. 1,290,757 to construct double-knife mower cutting systems in such a manner that the two oppositely moving mowing knives are supported on swing arms so that the knives are always resiliently pressed against each other in the cutting region. However, this construction has several deficiencies, especially since the swing arms rest directly on the mowing knives without a special thrust bearing and, for driving, surround engaging pieces 13 of the mowing knives. This metallic contact of the swing arms causes significant wear in all components, i.e., the swing arms, the knife blades, and the engaging pieces, as a result of the sliding frictional conditions which cannot be protected, especially under the influence of the sand and other dirt conditions during the mowing operation; as a result, these components become useless and must be replaced within a short time. This proposal has the further disadvantage that the swing arms cannot be adjusted with respect to their vertical positions and the pressure application on the mowing knives, and that, for replacing the knives, the swing arms must be raised in a cumbersome manner and removed in the raised position. For these reasons, these mower cutting systems were not widely accepted.
An improved mower cutting system of this type has been suggested in West German Patent No. 1,196,412, wherein the swing arms of a knife are arranged on resiliently acting swivel bearings which are adjustable with respect to the load application and by means of which the arms can be folded up for the exchange of knives. The swing arms of the other knife are supported through elastically acting swing arms which are vertically adjustable.
The known proposals for resiliently pressing swing arm supports for single-knife mower cutting systems, such as, for example, in accordance with West German Patent Nos. 803,685 and 1,119,581 and West German Utility Model No. 1,802,470, all have thrust swivel friction bearings which are also open at the bearing point between swinging lever and mowing knife and are usually subjected to a great wear at this point because the knife strokes are generally greater in single-knife mower cutting systems than in double-knife mower cutting systems.
In addition, in the known cutting systems, the knives are clasped by the swing arms so that the knives are swivable. However, every great and sudden load on the mowing knives during operation, for example, when the knives strike against solid resistance, is transmitted without damping to the swing arms, so that also these components are frequently damaged by bending or breaking. Furthermore, play in the bearing point between swing arm and mowing knife caused by the wear and reciprocating movements of the mowing knives with high frequency lead to a sudden pull on the guide arms whereby the driving forces are increased in a peak-like manner and the rivet joints between mowing knife blades and the mushroom-shaped projections which are engaged by the swing arms and between blades and mowing knife backs are also negatively affected, i.e., they soon become loose and then are completely destroyed which results in failure of the cutting systems and this, in turn, leads to long delays and expensive repairs. Furthermore, the secure support of the mowing knives suffers from the play in the bearings and from the loosening of the components; the arms frequently jump out of the mushroom-shaped projections and fall between the cutting edges of the blades, so that the blades and swing arms are damaged or, in most cases, destroyed.
In addition, the bearing play and the loose rivet joints of the components cause an annoying increase of the operating noise.
It is the primary object of the invention to provide, in mower cutting systems of the above-mentioned types, a construction of the thrust bearing between the swing arms and the mowing knife blades which eliminates any wear caused by sliding friction or dirty roller bearings or the like, is inexpensive and simple to maintain and insures an elastic and low-noise connection of the mowing knives and swing arms which is free of play.
In accordance with the invention, this object is met thereby that the thrust swivel bearing between the swing arm and the mowing knife is a rubber-metal block including internal and external bushings which are rigidly connected for rotation with the swing arm and the mowing knife, respectively, and an annular rubber portion disposed between the internal and external bushings, wherein one of these connections can be quickly disconnected in axial direction of the bushings.
In accordance with another proposal according to the invention, it is especially advantageous to provide the mowing knives with coupling pins which are conical and, for the torsional drive, are flattened, or are truncated pyramid-shaped or are polygonal in the cross section, the rubber-metal blocks which are rigidly mounted in the swing arms engaging over these coupling pins with their internal bushings in a form-closing manner.
In accordance with the invention, these coupling pins are constructed with respect to their side angles relative to each other in such a manner that the pairs of coupling parts are just short of the limit of self-locking whereby a secure and firm seat is achieved.
In accordance with the invention, the holes in the knife blades for riveting the coupling pins to the blades are also constructed noncircular or profiled, such as, for example, as an elliptic hole, an oblong hole, a polygonal hole or the like, so that, after riveting these pins to the blades, this connection remains fixed with respect to rotation also with respect to continuous load, even when the riveting should have loosened slightly.
In accordance with a special embodiment of the invention, a truncated pyramid-shaped coupling pin can also be produced by chipless shaping of the blade itself; this represents a simple and economical shape.
In accordance with another embodiment of the invention, the coupling pin is arranged on a support member which is connected to the rivets which connect the knife blades to the knife back, or is connected to the knife back through another, separate riveting. The support member and the coupling pin can be made of one piece, or they can be two separate pieces which are connected to each other by means of riveting or welding or the like. This is particularly advantageous because the mowing knife blades are parts which are subject to wear and must be replaced frequently and, in this manner, the coupling pin is always retained for the entire service life of the mowing knives and can even be removed from mowing knives which are to be scrapped and can be used again.
The rubber-metal block can also be constructed differently; for example, it can be forceably inserted or vulcanized with its rubber portion directly in the recess of the guide arm receiving the rubber-metal block, and the rubber portion can be connected to the internal bushing by vulcanizing. The rubber-metal block can also have an external bushing in the form of a tube or the like which, in accordance with a special proposal, is flanged at the side facing away from the knife blades for an axial contact with the end face of the rubber portion. Further, between the closed outer end face of the internal bushing and the bottom of the recess of the swing arm, a rubber plug may be concentrically inserted or vulcanized onto the internal bushing. In the latter embodiment, the rubber portion essentially transmits the radial forces and the rotation, while the rubber plug transmits the axial forces.
It is also possible to construct the external bushing and the internal bushing conical at their sides facing the rubber portion of the rubber-metal block, so that the radial and axial forces and the rotation can be safely transmitted by the rubber portion from the internal to the external bushing, wherein additional flanges can be provided on the external and internal bushings against which the rubber portion bears in the direction of load application. In these rubber-metal blocks, the rubber portions can be pressed between the internal and external bushings or they can be vulcanized onto the internal bushing or both bushings. For a secure support particularly in the case of rubber portions which are pressed in and for the time period without radial load, appropriate flanges can be provided at the edges of individual or all bushings.
In accordance with the invention, in cutting systems in which the swivel angle of the swing arms becomes great either because of great strokes of the knives or when relatively short swing arms must be used for reasons of space, the rubber portions are provided with appropriately thick walls, or rubber-metal double blocks are proposed in which the two rubber-metal blocks are arranged radially opposite each other, and it is possible to provide for transmitting the axial forces a rubber buffer, or rubber buffers for each block, in the center of the blocks.
In embodiments in which the rubber-metal block is fixedly arranged on the mowing knife, it is suggested in accordance with the invention to provide the swing arm with a cup-like coupling piece whose inner coupling hole is constructed conical, and wherein this cone, for transmitting the rotation forces, is profiled, for example, polygonal or with conically-shaped bulges, wherein the outer circumferential surface of the external bushing of the rubber-metal block is constructed as a counter-coupling piece in such a way that a form-closing connection is achieved.
When the rubber-metal block is fixedly arranged on the mowing knife, it is also possible to provide the end of the swing arm with a conical or wedge-like profiled pin which engages in a form-closing manner in an appropriately designed hole of the internal bushing of the rubber-metal block.
In swinging lever supports in which the rear swivel axis is approximately perpendicular and which are used in cutting systems in which the knives extend forwardly and downwardly under the conventional angle of about 4 to 8 degrees, it is proposed in accordance with the invention that the coupling pin or the rubber-metal block of the mowing knife also extends approximately perpendicular, i.e., approximately parallel with the rear support of the swinging lever on the back of the bar of the cutting system.
The invention is not limited to the recited examples with the respectively illustrated structural details; on the contrary, all the individually described and illustrated features can be utilized interchangeably without departing from the invention.
The advantages achieved with the invention reside particularly in the fact that, in the case of reciprocating mowing knives which are supported by means of swing arms, a non-wearing support is created for the thrust swivel bearing between the swing arm and the mowing knife, which support is simple in its construction, free of maintenance and additionally represents an axially and radially elastic connection between mowing knives and swing arms. This connection reduces the impact effects of the reciprocating system on all components and further acts as a restoring spring aiding in the drive of the mower knives because the rubber-metal block is tensioned for rotation during the second half of the stroke of the swivel motion and this tension supports the return stroke. Additionally a quick uncoupling of the bearing connection between swing arm and mowing knife which is free of play is possible, so that the exchange of knives can be performed easily and quickly and a low-noise support is created.